Cellulase has three types of enzyme activities: cellobiohydrolase activity which hydrolyzes the solid crystal regions of cellulose from the nonreduced end in an exo manner so as to generate cellobiose; endoglucanase activity which hydrolyzes the amorphous regions of cellulose in an endo manner so as to make cellulose molecules into low molecular weight molecules and to generate various types of cellooligosaccharides; and β-glucosidase activity which decomposes cellobiose or cellooligosaccharide into glucose. Of the enzymes, when endoglucanase exerts high activity, cellulase is advantageously used to treat fabric.
To impart certain desired properties to cellulose-containing fabric, the fabric has conventionally been treated with cellulase. For example, in the textile industry, treatment with cellulase is carried out to improve the touch and appearance of cellulose-containing fabric, or to impart “stonewash” appearance to colored cellulose-containing fabric thereby providing the fabric with localized color variation (EP Patent No. 307,564).
It is known that fuzz is developed on colored cellulose-containing fabric by repeated washing and that it blurs the color of the colored fabric. A cellulase-containing detergent removes such fuzz and makes the color of the fabric clear (color clarification) (EP Patent No. 220,016), and therefore detergents containing cellulase are currently on the market mainly in Europe and the United States.
In such textile processing, cellulase derived from wood-rotting fungi such as Trichoderma and Humicola is mainly used. Such cellulase is used as a mixture comprising multiple cellulase components which is obtained by processing a culture filtrate of microorganisms having cellulolytic activity. However, in order to achieve greater economy, a cellulase preparation obtained by isolating from cellulase components, only endoglucanase which largely acts on fabric treatment, and genetically enhancing it, has recently been used. Examples of such endoglucanase with high activity include: EGV (JP Patent Publication (PCT Translation) No. 5-509223) and NCE4 (WO98/03640) derived from Humicola insolens, which strongly act on cotton fabrics; RCE I, RCE II and RCE III derived from Rhizopus oryzae, which strongly act on lyocell fabrics; MCE I and MCE II derived from Mucor circinelloides; and PCE I derived from Phycomyces nitens (WO00/24879).
In order to improve the effects of cellulase, the combined use of additives has also been attempted. For example, JP Patent Publication (PCT Translation) No. 5-507615 describes that a water-soluble polymer such as polyvinylpyrrolidone, polyvinyl alcohol and polyacrylamide enhances the effects of Humicola insolens-derived cellulase and improves its activity of removing fuzz from colored fabric. Moreover, it is known that CMCase activity in the culture solution of Trichoderma viride is improved by the addition of Tween 20 (Ooshima, H. et al., Biotechnology and Bioengineering 28: 1727–1734, 1986).
However, the cellulases used for the above-described purposes are all expensive. Therefore, in order to achieve an industrial level application, further improvement of endoglucanase activity is desired, so that the above effects of cellulase can be more efficiently exerted.